In a lane assist system of the above-mentioned type, the lane ahead or beneath the vehicle is detected by a surround sensor. If the vehicle threatens to depart the lane to the right or the left, an acoustic, a visual and/or a haptic warning is output to the driver.
Another possible application of a lane assist system of the above-mentioned type arises when driving on a multi-lane roadway when the driver intends to depart the right lane and change over to the middle lane or the left lane in order to pass a slower moving vehicle traveling ahead. If, at the beginning of the steering process, the surround sensor detects a vehicle rapidly approaching from the rear, the driver is prompted by an acoustic, visual and/or haptic warning to abort the lane change operation.
The lane assist system typically has a sensor system which is made up of a two-dimensional sensor array or only one or a few sensor row(s). As a rule, the sensor system is mounted on the vehicle's front, pointing ahead, and scans a certain roadway section in the vehicle's surroundings. The obtained image information is analogously or digitally processed using known technologies in order to extract information about the roadway markings and the roadway edge. In the event of the vehicle threatening to depart the current lane under danger, the warning device outputs an acoustic, visual and/or haptic alert.
An acoustic alert, for example, may be output in the form of a sound, known as a spike strip rattling sound, specifically on the vehicle side on which the vehicle threatens to depart the lane. Such a spike strip rattling sound acoustically simulates the crossing of a roadway marking provided with spikes or a profile. As a response to this sound, the driver may for the most part intuitively very quickly carry out a suitable steering correction. However, such an acoustic alert has the disadvantage that the other vehicle passengers are often intensely disturbed and unsettled.
In the case of a haptic alert, e.g., vibration of the steering wheel, the disturbance of the other vehicle passengers is avoided, but such a vibration alert is not direction-specific, so that the driver is not able to carry out an intuitive targeted steering correction. Rather, the driver, alarmed by the alert, must initially visually comprehend the instantaneous situation and then initiate an appropriate response. As a result, valuable split seconds are often lost, particularly in critical traffic situations.